CN113363671A - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
- Publication number
- CN113363671A CN113363671A CN202110735611.0A CN202110735611A CN113363671A CN 113363671 A CN113363671 A CN 113363671A CN 202110735611 A CN202110735611 A CN 202110735611A CN 113363671 A CN113363671 A CN 113363671A
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- China
- Prior art keywords
- functional layer
- electrochemical device
- electrolyte
- active material
- pole piece
- Prior art date
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- 239000000463 material Substances 0.000 claims abstract description 8
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- 239000007774 positive electrode material Substances 0.000 claims description 26
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- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 229920001684 low density polyethylene Polymers 0.000 description 1
- 239000004702 low-density polyethylene Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000002931 mesocarbon microbead Substances 0.000 description 1
- 229940017219 methyl propionate Drugs 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- YKYONYBAUNKHLG-UHFFFAOYSA-N n-Propyl acetate Natural products CCCOC(C)=O YKYONYBAUNKHLG-UHFFFAOYSA-N 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 125000006353 oxyethylene group Chemical group 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 229940090181 propyl acetate Drugs 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000007613 slurry method Methods 0.000 description 1
- 229910021384 soft carbon Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0034—Fluorinated solvents
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte, the isolating membrane is arranged between the positive pole piece and the negative pole piece, the isolating membrane comprises a base material and a functional layer positioned on at least one surface of the base material, the electrochemical device meets the condition that A/H is more than or equal to 0.048 and less than or equal to 4.5, and H [ mu ] m is the thickness of the functional layer; a mg/mAh is the liquid retention coefficient of the electrolyte. The isolating membrane of the electrochemical device contains a large amount of electrolyte, the low-temperature circulation interface between the electrode pole piece and the isolating membrane is improved, the internal resistance of the electrochemical device is reduced, and therefore the high-rate circulation performance of the electrochemical device under the low-temperature condition is obviously improved.
Description
Technical Field
The present disclosure relates to electrochemical technologies, and particularly to an electrochemical device and an electronic device.
Background
The lithium ion battery has the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, good safety and the like, and is widely applied to various fields of portable electric energy storage, electronic equipment, electric automobiles and the like.
With the continuous progress of the lithium ion battery technology, the charging speed of the lithium ion battery is faster and faster, but the lower limit of the normal use temperature of the lithium ion battery is lower, which causes the lithium ion battery to be easy to generate a lithium separation phenomenon on the negative electrode in a low-temperature high-rate charging scene, and further deteriorates the low-temperature high-rate cycle performance of the lithium ion battery. Therefore, how to improve the large-rate cycle performance of the lithium ion battery at low temperature is a problem to be solved urgently.
Disclosure of Invention
An object of the present application is to provide an electrochemical device and an electronic device to improve the high-rate cycle performance of the electrochemical device at low temperature.
The first aspect of the application provides an electrochemical device, including positive pole piece, negative pole piece, barrier film and electrolyte, the barrier film sets up between positive pole piece and negative pole piece, and the barrier film includes the substrate and is located the functional layer on at least one surface of substrate, wherein, electrochemical device satisfies 0.048 and is less than or equal to A/H and is less than or equal to 4.5, and H mu m does the thickness of functional layer, and A mg mAh does the liquid retention coefficient of electrolyte. By controlling the A and the H to meet the relationship, a proper amount of electrolyte can be stored in the isolating membrane, the low-temperature circulation interface between the negative pole piece and the isolating membrane is improved, the internal resistance of the electrochemical device is reduced, and the high-rate circulation performance of the electrochemical device under the low-temperature condition is improved.
In one embodiment of the present application, the electrochemical device satisfies at least one of conditions (a) or (b): (a) a is more than or equal to 1.2 and less than or equal to 4.5; (b) h is more than or equal to 1 and less than or equal to 25. By controlling the liquid retention coefficient a of the electrolyte and the thickness H of the functional layer in the above ranges, the high-rate cycle performance of the electrochemical device at low temperatures can be further improved.
In one embodiment of the present application, the negative electrode tab comprises a negative electrode current collector and a negative electrode active material layer,a first functional layer is provided on a surface of the substrate facing the negative electrode active material layer, and at least one of conditions (c) to (f) is satisfied: (c) the thickness of the first functional layer is H1 mu m, and H1 is more than or equal to 2 and less than or equal to 15; (d) the first functional layer comprises a first polymer having an average particle diameter of 1.5 to 15 μm; (e) the first functional layer comprises a first polymer comprising at least one of a homopolymer or copolymer of vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, chloropropene, acrylic acid, an acrylate, styrene, butadiene, and acrylonitrile; (f) the mass of the first functional layer is 2mg/5000mm2To 10mg/5000mm2. By controlling the thickness of the first functional layer within the above range, the kinetic performance and energy density of the electrochemical device can be further improved; by controlling the average particle size of the first polymer within the range, the electrolyte transmission channel can be widened, the electrolyte wettability of the electrochemical device is improved, and the low-temperature cycle performance is better; by controlling the monomer composition of the polymer, a first polymer meeting the requirements can be obtained; by controlling the quality of the first functional layer in the range, the separator and the electrode plate have excellent interfacial adhesion performance, and the influence on the energy density of the electrochemical device is small.
In one embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and a second functional layer is provided on a surface of the substrate facing the positive electrode active material layer, and at least one of the conditions (g) to (j) is satisfied: (g) the thickness of the second functional layer is H2 mu m, and H2 is more than or equal to 0.5 and less than or equal to 10; (h) the adhesion between the separator and the negative electrode active material layer is N1, and the adhesion between the separator and the positive electrode active material layer is N2, N1<N2; (i) the mass of the second functional layer is 0.3mg/5000mm2To 5mg/5000mm2(ii) a (j) The second functional layer comprises a second polymer, and the second polymer comprises ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, ethyl methacrylate, butyl methacrylate, ethylene, chlorostyreneAt least one of homopolymers or copolymers of an alkene, a fluorostyrene, a methylstyrene, an acrylonitrile or a methacrylonitrile. By controlling the above parameters, the dynamic performance and low temperature performance of the electrochemical device can be further improved.
In an embodiment of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, one side of the substrate facing the negative electrode active material layer is provided with a first functional layer, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, one side of the substrate facing the positive electrode active material layer is provided with a second functional layer, at least one of the first functional layer and the second functional layer and a third functional layer between the substrate, the third functional layer includes inorganic particles, and at least one of the conditions (k) to (l) is satisfied: (k) the third functional layer has a thickness of 0.2 to 6 μm; (l) The inorganic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or silicon nitride.
In one embodiment of the present application, the electrolyte includes a chain carboxylic ester and fluoroethylene carbonate, the chain carboxylic ester is present in an amount of X% by mass and the fluoroethylene carbonate is present in an amount of Y% by mass based on the total mass of the electrolyte, and the relationship between X and Y satisfies: X/Y is more than or equal to 0.5 and less than or equal to 30.
In one embodiment of the present application, the chain carboxylic acid ester includes a compound represented by structural formula (1):
wherein R is1Selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms, a substituted or unsubstituted chain alkenyl group having 2 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 15 carbon atomsRadical, R2Selected from substituted or unsubstituted alkyl groups having 1 to 5 carbon atoms, substituted or unsubstituted chain alkenyl groups having 2 to 6 carbon atoms, and substituted or unsubstituted aryl groups having 6 to 15 carbon atoms; when each group is substituted, the substituent is selected from hydrogen atom, halogen atom, hydroxyl, methyl, ethyl, propyl, butyl, vinyl, phenyl, phenoxy; based on the total mass of the electrolyte, the mass percentage of the chain carboxylic ester is 5-60%.
In one embodiment herein, the carboxylic acid ester comprises at least one of ethyl acetate, propyl propionate, ethyl propionate.
In one embodiment of the present application, 1. ltoreq. Y.ltoreq.18.
In one embodiment of the present application, 6 ≦ Y ≦ 18.
In one embodiment of the present application, the electrolyte further includes at least one of a sultone compound, a dinitrile compound, a trinitrile compound, or lithium difluorophosphate; based on the total mass of the electrolyte, the mass percentage of the sultone compound is 0.01-6%, and/or the mass percentage of the dinitrile compound is 0.1-10%, and/or the mass percentage of the dinitrile compound is 0.1-5%, and/or the mass percentage of the lithium difluorophosphate is 0.01-1%.
In one embodiment of the present application, the sultone compound includes any one of the following formulas (1-1) to (1-8):
the dinitrile compound includes any one of the following formulae (2-1) to (2-4):
the trinitrile compound includes any one of the following formulae (3-1) to (3-3):
the present application also provides an electronic device comprising any of the electrochemical devices described herein.
Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.
Drawings
In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces examples and figures that need to be used in the prior art, it being obvious that the figures in the following description are only some examples of the present application.
Fig. 1 is a schematic view of a structure of a separation membrane in an electrochemical device according to a first embodiment of the present application;
fig. 2 is a schematic view of a structure of a separation film in an electrochemical device according to a second embodiment of the present application;
fig. 3 is a schematic view of the structure of a separation membrane in an electrochemical device according to a third embodiment of the present application;
fig. 4 is a schematic view of the structure of a separation membrane in an electrochemical device according to a fourth embodiment of the present application.
In the figure, 1, a substrate, 2, a first functional layer, 3, a second functional layer, 4, a third functional layer, and 5, a first auxiliary adhesive.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other technical solutions obtained by a person of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.
In the embodiments of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
The first aspect of the application provides an electrochemical device, which comprises a positive pole piece, a negative pole piece, an isolation film and electrolyte, wherein the isolation film is arranged between the positive pole piece and the negative pole piece and comprises a substrate and a functional layer positioned on at least one surface of the substrate, the electrochemical device satisfies the conditions that A/H is more than or equal to 0.048 and less than or equal to 4.5, H mu m is the thickness of the functional layer, and A mg/mAh is the liquid retention coefficient of the electrolyte. For example, a/H may be 0.05, 0.1, 0.3, 0.5, 0.7, 1.0, 1.5, 1.7, 1.9, 2.0, 2.3, 2.5, 3.0, 3.2, 4.5, or any range therebetween. Without being limited to any theory, the inventor researches and discovers that when the value of A/H is too small (for example, less than 0.048), the liquid retention coefficient of the electrolyte is too small, the thickness of the functional layer is too large, and the retention amount of the electrolyte of the isolating membrane is influenced; if the value of a/H is too large (for example, more than 4.5), the retention coefficient of the electrolyte is too large and the thickness of the functional layer is too small, which also affects the retention amount of the electrolyte in the separator. By controlling the A and the H to meet the relationship, a large amount of electrolyte can be stored in the isolating membrane, the low-temperature circulating interface between the positive pole piece and/or the negative pole piece and the isolating membrane is improved, the internal resistance of the electrochemical device is reduced, and the high-rate circulating performance of the electrochemical device under the low-temperature condition is improved.
In one embodiment of the present application, the electrochemical device of the present application satisfies at least one of conditions (a) or (b): (a) a is more than or equal to 1.2 and less than or equal to 4.5; (b) h is more than or equal to 1 and less than or equal to 25. For example, a may be 1.2, 1.3, 1.5, 1.7, 1.9, 2.0, 2.5, 2.7, 3.0, 3.5, 4.0, 4.5, or any range therebetween. H may be 1, 2, 2.5, 3.0, 3.5, 4, 4.5, 5, 6, 7, 9, 11, 13, 15, 18, 20, 22, 25, or any range therebetween. By controlling the liquid retention coefficient a of the electrolyte and the thickness H of the functional layer in the above ranges, the high-rate cycle performance of the electrochemical device at low temperatures can be further improved.
In one embodiment of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and a first functional layer is provided on a side of the substrate facing the negative electrode active material layer, the electrochemical device of the present application satisfies at least one of the following conditions (c) to (f): (c) the thickness of the first functional layer is H1 μm, and H1 is more than or equal to 2 and less than or equal to 15; (d) the first functional layer comprises a first polymer having an average particle diameter of 1.5 to 15 μm; (e) the first functional layer comprises a first polymer comprising at least one of a homopolymer or copolymer of vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, chloropropene, acrylic acid, an acrylate, styrene, butadiene, and acrylonitrile; (f) the mass of the first functional layer is 2mg/5000mm2To 10mg/5000mm2。
The surface of the substrate facing the negative active material layer can be provided with a first functional layer, the thickness of the first functional layer is H1 mu m, and H1 is more than or equal to 2 and less than or equal to 15. For example, the thickness H1 of the first functional layer may be 2, 3, 4, 6, 8, 10, 12, 15 or any range therebetween. Without being limited to any theory, when the thickness H1 of the first functional layer is too small (for example, less than 2 μm), the wetting of the electrolyte between the functional layers is affected, which is not favorable for improving the dynamic performance of the electrochemical device; when the thickness H1 of the first functional layer is too large (for example, greater than 15 μm), the ion transport distance is increased, which affects the dynamic performance of the electrochemical device and is not favorable for increasing the energy density of the battery. By controlling the thickness of the first functional layer within the above range, the kinetic performance and energy density of the electrochemical device can be further improved.
The first polymer herein has an average particle size of 1.5 μm to 15 μm. For example, the first polymer may have an average particle size of 1.5 μm, 2.0 μm, 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, or any range therebetween. The average particle size of the first polymer may be determined by laser particle sizer or scanning electron microscope testing. Without being bound by any theory, when the average particle size of the first polymer is too small (e.g., less than 1.5 μm), the first polymer particles are easily agglomerated, affecting the kinetic performance of the electrochemical device; when the average particle size of the first polymer is too large (for example, larger than 15 μm), the adhesive strength of the first polymer is liable to be lowered, which is disadvantageous in improving the adhesive performance of the first functional layer. By controlling the average particle size of the first polymer within the range, the electrolyte transmission channel can be widened, the electrolyte wettability of the electrochemical device is improved, and the low-temperature cycle performance is better.
The first polymer is not particularly limited as long as the object of the present application can be achieved. Illustratively, the first polymer may comprise at least one of a homopolymer or copolymer of vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, chloropropene, acrylic acid, acrylate, styrene, butadiene, and acrylonitrile.
The first functional layer may be present in the form of islands in the present application.
In the present application, the first functional layer has a mass of 2mg/5000mm2To 10mg/5000mm2. For example, the first functional layer may have a mass of 2mg/5000mm2、3mg/5000mm2、5mg/5000mm2、8mg/5000mm2、10mg/5000mm2Or any range therebetween. Without being bound by any theory, when the first functional layer mass is too low (e.g., less than 2mg/5000 mm)2) The adhesion between the separator and the negative electrode is insufficient, and the adhesion performance of the first functional layer is reduced; when the first functional layer has too high a mass (e.g. higher than 10mg/5000 mm)2) The relative content of the electrode active material in the electrochemical device is decreased, affecting the energy density of the electrochemical device. By controlling the quality of the first functional layer in the range, the separator and the electrode plate have excellent interfacial adhesion performance, and the influence on the energy density of the electrochemical device is small. The "first functional layer quality" refers to the weight of the first functional layer provided on one surface of the separator.
In one embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and a second functional layer is provided on a surface of the substrate facing the positive electrode active material layer, and satisfies at least one of the conditions (g) to (j): (g) the thickness of the second functional layer is H2 μm, and H2 is more than or equal to 0.5 and less than or equal to 10; (h) the adhesion between the separator and the negative electrode active material layer was N1,the adhesion between the separator and the positive electrode active material layer was N2, N1<N2; (i) the second functional layer has a mass of 0.3mg/5000mm2To 5mg/5000mm2(ii) a (j) The second functional layer comprises a second polymer comprising at least one of a homopolymer or copolymer of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, ethyl methacrylate, butyl methacrylate, ethylene, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile, or methacrylonitrile.
The surface of the substrate facing the positive electrode active material layer may be provided with a second functional layer. Without being limited to any theory, when the value of the thickness H2 of the second functional layer is too small (e.g., less than 0.5 μm), the interfacial adhesion is insufficient and the functional layer adhesion performance is degraded; when the thickness H2 of the second functional layer is excessively large (e.g., greater than 10 μm), the lithium ion transport distance in the separator is increased, affecting the kinetic performance of the electrochemical device. By controlling the thickness of the second functional layer within the range, the separator and the negative pole piece can have good interfacial bonding performance, and the dynamic performance of the electrochemical device is further improved.
The adhesion between the separator and the negative electrode active material layer is N1, the adhesion between the separator and the positive electrode active material layer is N2, and N1 is less than N2. For example, N1< N2 < 15N1, N1< N2 < 10N1, and N1< N2 < 8N1 can be used. By controlling N1< N2, the low temperature cycle performance of the electrochemical device can be further improved.
The adhesive force between the isolating membrane and the negative active material layer is N1, and the requirement that N1 is more than or equal to 0.5N/m and less than or equal to 7N/m is met. For example, it may be 1N/m, 3N/m, 5N/m, 7N/m or any range therebetween.
The adhesive force between the isolating film and the positive active material layer is N2, and the requirement that N2 is more than or equal to 1N/m and less than or equal to 15N/m is met. For example, 1N/m, 3N/m, 5N/m, 7N/m, 9N/m, 10N/m, 12N/m, 15N/m or any range therebetween.
In the present application, the second functional layer may be present in the form of islands.
In the present application, the second functional layer has a mass of 0.3mg/5000mm2To 5mg/5000mm2. For example, the second functional layer may have a mass of 0.3mg/5000mm2、0.5mg/5000mm2、0.7mg/5000mm2、1mg/5000mm2、2mg/5000mm2、2.5mg/5000mm2、3mg/5000mm2、5mg/5000mm2Or any range therebetween. The "second functional layer quality" refers to the weight of the second functional layer provided on one surface of the separator. Without being bound by any theory, when the second functional layer mass is too low (e.g., less than 0.3mg/5000 mm)2) The adhesive force between the interfaces is insufficient, and the adhesive performance of the second functional layer is reduced; when the second functional layer has too high a mass (e.g. above 5mg/5000 mm)2) And the lithium ion transmission channel is easy to block, and the multiplying power performance of the electrochemical device is influenced. By controlling the quality of the second functional layer in the range, the separator and the positive pole piece have excellent interfacial adhesion performance, gas generation side reaction between the electrolyte and the positive pole piece under a high-temperature condition is inhibited, the high-temperature storage and cycle performance of the electrochemical device is improved, and the influence on the rate performance of the electrochemical device is small.
The second polymer is not particularly limited as long as the object of the present application can be achieved. For example, the second polymer may include at least one of homopolymers or copolymers of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, ethyl methacrylate, butyl methacrylate, ethylene, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile, or methacrylonitrile.
The second polymer herein has an average particle size of 0.3 μm to 4 μm. For example, it may be 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm or any range therebetween.
The average particle size of the first polymer is herein greater than the average particle size of the second polymer. The average particle size can be obtained by adopting a laser particle sizer or a scanning electron microscope for testing.
In one embodiment of the present application, a third functional layer is between the substrate and at least one of the first functional layer and the second functional layer, the third functional layer comprising inorganic particles. The electrochemical device of the present application satisfies at least one of the following conditions (k) to (l): (k) the thickness of the third functional layer is 0.5 to 6 μm; (l) The inorganic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or silicon nitride.
In the application, the third functional layer is arranged between the substrate and at least one of the first functional layer and the second functional layer, so that the mechanical strength of the isolating membrane is improved. Illustratively, a third functional layer is provided between the first functional layer and the substrate; or a third functional layer is arranged between the second functional layer and the base material; or third functional layers are arranged between the first functional layer and the base material and between the second functional layer and the base material.
The third functional layer of the present application has a thickness of 0.5 to 6 μm. For example, it may be 0.5 μm, 1 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm or any range therebetween. Without being limited to any theory, when the thickness of the third functional layer is too low (e.g., less than 0.5 μm), the mechanical strength of the separator is reduced, which is not favorable for the improvement of the cycle performance of the electrochemical device; when the thickness of the third functional layer is too high (e.g., higher than 6 μm), the separator becomes thick as a whole, and the relative content of the electrode active material decreases, which is not favorable for increasing the energy density of the electrochemical device. By controlling the thickness of the third functional layer within the above range, the electrochemical device can have high cycle performance and energy density.
The inorganic particles of the third functional layer are not particularly limited as long as the object of the present application can be achieved. In one embodiment of the present application, the inorganic particles may comprise at least one of alumina, boehmite, titania, silica, zirconia, tin dioxide, magnesium hydroxide, magnesia, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or silicon nitride.
In one embodiment of the present application, the second polymer may include a core-shell structured high molecular polymer or a non-core-shell structured high molecular polymer. The core-shell structure polymer and the non-core-shell structure polymer are not particularly limited, and for example, the core main component of the core-shell structure polymer may be a polymer, and the polymer may be a homopolymer obtained by polymerizing one polymerizable monomer or a copolymer obtained by polymerizing two or more polymerizable monomers. Specifically, the core of the high molecular polymer with the core-shell structure comprises at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid or maleic acid; the shell of the core-shell structure high molecular polymer may be a homopolymer of one polymerizable monomer or a copolymer of two or more polymerizable monomers, and the polymerizable monomer may include an acrylic ester, an aromatic monovinyl compound or a vinyl cyanide compound. Specifically, the shell of the high molecular polymer of the core-shell structure includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile, or methacrylonitrile. The high molecular polymer with the non-core-shell structure comprises at least one of acrylic acid, acrylate, butadiene, styrene, acrylonitrile, ethylene, chlorostyrene, fluorostyrene or propylene.
In one embodiment of the present application, the surface of the barrier film substrate includes a first functional layer and a second functional layer, and a third functional layer is included between the first functional layer and the barrier film substrate, the first functional layer can retain electrolyte through a space between polymers, the second functional layer gives the barrier film good adhesive property through a binder, and the third functional layer establishes physical separation between a positive electrode and a negative electrode through inorganic particles to prevent short circuit. The three components act together, so that when the isolating membrane is used in an electrochemical device, the isolating membrane and a negative pole piece have good interfacial bonding performance, the liquid retention coefficient of electrolyte is improved, and the dynamic performance of the electrochemical device is improved.
In one embodiment of the present application, the electrolyte comprises chain carboxylic ester and fluoroethylene carbonate (FEC), wherein the chain carboxylic ester is present in an amount of X% by mass and the fluoroethylene carbonate is present in an amount of Y% by mass, based on the total mass of the electrolyte, and the relationship between X and Y satisfies: X/Y is more than or equal to 0.5 and less than or equal to 30. For example, it may be 0.5, 1,3, 5, 7, 10, 13, 15, 17, 20, 25, 30 or any range therebetween. From the perspective of improving the rate performance of the electrochemical device at low temperature, by controlling the ratio of X and Y within the range, the chain carboxylate can effectively improve the dynamic performance of the electrolyte and improve the deposition of lithium ions of the negative electrode plate at low temperature during high-rate charging; the fluoroethylene carbonate can effectively form a film on the surface of the negative pole piece, and can also improve the deposition of lithium ions of the negative pole piece at low temperature during high-rate charging, thereby synergistically improving the low-temperature cycle performance of the electrochemical device.
In one embodiment of the present application, the chain carboxylic acid ester includes a compound represented by structural formula (1):
wherein R is1Selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms, a substituted or unsubstituted chain alkenyl group having 2 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 15 carbon atoms, R2Selected from the group consisting of a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted chain alkenyl group having 2 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 15 carbon atoms. When each group is substituted, the substituent may be selected from a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a propyl group, a butyl group, a vinyl group, a phenyl group, and a phenoxy group.
Illustratively, the chain carboxylic acid ester may include, but is not limited to, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate.
In one embodiment of the present application, the content of the chain carboxylic acid ester is 5 to 60% by mass based on the total mass of the electrolyte. Without being limited to any theory, the electrolyte has high conductivity by controlling the mass percentage of the chain carboxylate in the electrolyte within the range, and the function of improving the dynamic performance of the electrolyte by the chain carboxylate is effectively exerted, so that the high-rate cycle performance of the electrochemical device under the low-temperature condition is improved.
In one embodiment of the present application, the electrolyte solution contains chain carbonate and chain carboxylate, and the sum of the weight percentages of the chain carbonate and the chain carboxylate is 30% to 65% based on the total weight of the electrolyte solution. The sum of the contents of the two components is controlled within the range, so that the capacity retention rate of the electrochemical device can be maintained, and the gas generation of the electrochemical device can be reduced.
In one embodiment of the present application, the fluoroethylene carbonate is present in an amount of 1 to 18% by mass, based on the total mass of the electrolyte. For example, it may be 1%, 3%, 5%, 7%, 9%, 10%, 12%, 15%, 18% or any range therebetween.
In one embodiment of the present application, the fluoroethylene carbonate is present in an amount of 6 to 18% by mass, based on the total mass of the electrolyte. For example, it may be 6%, 8%, 10%, 12%, 15%, 18%, or any range therebetween.
In one embodiment of the present application, the electrolyte further includes at least one of a sultone compound, a dinitrile compound, a trinitrile compound, or lithium difluorophosphate.
In one embodiment of the present application, the sultone compound is present in an amount of 0.01 to 6% by mass based on the total mass of the electrolyte. For example, it may be 0.01%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 2%, 3%, 5%, 6%, or any range therebetween. Without being limited to any theory, by controlling the content of the sultone compound in the electrolyte within the above range, the sultone compound can protect the structure of the positive electrode sheet during the circulation process of the electrochemical device, and can reduce the direct current internal resistance increase rate (DCR) of the electrochemical device and improve the circulation performance of the electrochemical device. However, the content of the sultone compound should not be too low or too high, and when it is too low (e.g., less than 0.01%) the protective effect is not significant, and when it is too high (e.g., more than 6%) the protective effect is improved to a limited extent.
In one embodiment of the present application, the mass percentage of dinitrile compound is between 0.1% and 10%. For example, it may be 0.1%, 1%, 2%, 3%, 5%, 6%, 8%, 10% or any range therebetween. According to the method, the content of the dinitrile compound in the electrolyte is controlled within the range, and the dinitrile compound can stabilize the lattice cobalt of the positive active material, so that the structure of the positive pole piece is protected in the circulation process of the electrochemical device. However, the content of the dinitrile compound should not be too low or too high, the protective effect is not obvious when the content is too low (for example, less than 0.1%), and when the content is too high (for example, more than 10%), the viscosity of the electrolyte is affected, so that the direct current internal resistance increase rate of the electrochemical device is increased, and the protective effect of the sultone compound on the positive electrode plate is counteracted.
In one embodiment of the present application, the amount of the trinitrile compound is 0.1% to 5% by mass, and for example, may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 5% or any range therebetween. By controlling the content of the trinitrile compound in the electrolyte within the above range, the trinitrile compound can stabilize the lattice structure of the positive active material, and has a synergistic effect when being matched with the dinitrile compound, so that the low-temperature cycle performance of the electrochemical device is further improved. However, the content of the trinitrile compound is also not suitable to be too low or too high, the protection effect is not obvious when the content is too low (for example, less than 0.1%), and when the content is too high (for example, more than 5%), the viscosity of the electrolyte is influenced, so that the direct current internal resistance increase rate of the electrochemical device is increased, and the protection effect of the sultone compound on the positive electrode plate is reduced.
In one embodiment of the present application, the lithium difluorophosphate is present in an amount of 0.01% to 1% by mass, for example, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1% or any range therebetween. According to the lithium difluorophosphate battery, the content of lithium difluorophosphate in the electrolyte is controlled within the range, the lithium difluorophosphate can form a film on the surface of the negative pole piece, the film forming impedance is low, and the direct current internal resistance increase rate of the electrochemical device can be reduced. However, the content of lithium difluorophosphate should not be too low or too high, and when it is too low (for example, less than 0.01%), the effect of reducing the increase rate of the direct current internal resistance is not significant, and when it is too high (for example, less than 1%), the degree of reduction of the increase rate of the direct current internal resistance is limited.
It can be seen that the electrochemical device having excellent rate performance under low temperature conditions can be obtained by controlling the contents of the sultone compound, and/or the dinitrile compound, and/or the trinitrile compound, and/or the lithium difluorophosphate in the electrolyte to be within the above ranges.
The sultone compound is not particularly limited herein, and, for example, the sultone compound may include any one of the following formulas (1-1) to (1-8):
the dinitrile compound is not particularly limited herein, and illustratively, the dinitrile compound may include any one of the following formulae (2-1) to (2-4):
the nitrile compound is not particularly limited herein, and illustratively, the nitrile compound may include any one of the following formulas (3-1) to (3-3):
the first functional layer of the present application may further include a first auxiliary adhesive therein. In one embodiment, the first polymer is contained in an amount of 85 to 95% by mass and the first auxiliary binder is contained in an amount of 5 to 15% by mass, based on the total mass of the first functional layer, so that the first functional layer having excellent adhesive properties can be obtained. The first auxiliary adhesive is not particularly limited, and may include, for example, at least one of homopolymers or copolymers of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, and butadiene.
In the application, the second functional layer further comprises a first compound, and the first compound can effectively reduce the surface energy of the second functional layer slurry and is beneficial to coating and forming of the second functional layer on the isolating film. The first compound comprises at least one of dimethyl siloxane, polyethylene oxide, ethylene oxide alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer and dioctyl sodium sulfosuccinate.
At least one of a carboxymethyl cellulose compound, a second auxiliary binder, and a first compound may be further included in the second functional layer of the present application. The carboxymethyl cellulose compound can increase the stability of the slurry of the second functional layer and prevent the slurry from settling. The carboxymethyl cellulose compound of the present application may be at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. The second auxiliary adhesive functions as an auxiliary adhesive to further improve the adhesion property of the second functional layer. The second auxiliary adhesive is not particularly limited as long as the object of the present application can be achieved, and for example, the second auxiliary adhesive may include at least one of homopolymers or copolymers of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, or butadiene. The first compound may reduce the surface energy of the slurry, and the first compound may include at least one of dimethylsiloxane, polyethylene oxide, an oxyethylene alkylphenol ether, a polyoxyethylene fatty alcohol ether, a polyoxyethylene polyoxypropylene block copolymer, or dioctyl sodium sulfosuccinate. In one embodiment, the second polymer is present in an amount of 88 to 99.5 percent by mass, based on the total mass of the second functional layer. In one embodiment, the carboxymethyl cellulose compound is present in an amount of 0.5 to 2% by mass, based on the total mass of the second functional layer. In one embodiment, the first compound is contained in an amount of 7 to 10% by mass based on the total mass of the second functional layer, and the second functional layer having excellent adhesion properties can be obtained.
The method for preparing the first polymer of the present application is not particularly limited, and a method for preparing the first polymer by a person skilled in the art may be employed, and for example, the following method may be employed:
vacuumizing the reaction kettle, after nitrogen is pumped to replace oxygen, adding deionized water, reaction monomers, an initiator, an emulsifier perfluoroalkyl carboxylate and a chain transfer agent isopropanol into the reaction kettle containing a stirrer until the pressure of the reaction kettle is about 3.5 MPa. And then heating to 50-70 ℃, rotating the stirrer at a speed of 70-100 r/min, starting a polymerization reaction, continuously adding reaction monomers, keeping the pressure of the reaction kettle at 3.5MPa, stopping the reaction until the solid content of the emulsion in the reactor reaches 25-30%, recovering unreacted monomers, discharging the polymer emulsion, centrifuging, washing and drying to obtain the first polymer.
The initiator is not particularly limited as long as it can initiate polymerization of the monomer, and may be, for example, diisopropylbenzene hydroperoxide. The addition amounts of the monomer, the deionized water, the initiator and the chain transfer agent are not particularly limited, as long as the added monomer is ensured to perform a polymerization reaction, for example, the deionized water is 5 times to 10 times of the mass of the monomer, the initiator accounts for 0.05% to 0.5% of the mass of the monomer, the emulsifier accounts for 0.1% to 1% of the mass of the monomer, and the chain transfer agent accounts for 3% to 7% of the mass of the monomer.
The method for preparing the second polymer of the present application is not particularly limited, and a method for preparing the second polymer by a person skilled in the art may be employed, and for example, the following method may be employed:
adding distilled water into a reaction kettle, starting stirring, introducing nitrogen to remove oxygen, adding at least one of monomers such as ethyl acrylate, butyl acrylate, ethyl methacrylate and the like according to different mass ratios, heating to about 65 ℃ under an inert atmosphere, keeping the temperature constant, then adding an initiator to initiate reaction, and finishing the reaction after about 20 hours.
The initiator is not particularly limited as long as it can initiate polymerization of the monomers, and may be, for example, a 20% ammonium persulfate solution. The amount of the distilled water and the initiator added is not particularly limited as long as the polymerization of the added monomers is ensured. After the reaction, alkali liquor can be added into the precipitate of the reaction for neutralization, so that the pH value is 6.5-9. The reaction product can also be filtered, washed, dried, crushed, sieved and the like.
The method for preparing the first auxiliary adhesive and the second auxiliary adhesive is not particularly limited, and may be a method commonly used by those skilled in the art, and may be selected according to the kind of the monomer used, for example, a solution method, a slurry method, a gas phase method, etc.
The present application is not particularly limited in the method for producing the third functional layer, and the third functional layer may be formed, for example, by applying a slurry containing inorganic particles to the surface of the release film substrate.
The positive electrode sheet in the present application includes a positive current collector and a positive active material layer. The positive electrode current collector is not particularly limited, and may be any positive electrode current collector in the art, such as an aluminum foil, an aluminum alloy foil, or a composite current collector. The positive electrode active material layer includes a positive electrode active material, the positive electrode active material is not particularly limited, and any positive electrode active material in the art may be used, and for example, may include at least one of lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, a lithium rich manganese-based material, lithium cobalt oxide, lithium manganese iron phosphate, or lithium titanate.
The negative electrode sheet in the present application contains a negative electrode current collector and a negative electrode active material layer. Among them, the negative electrode collector is not particularly limited, and any negative electrode collector in the art, such as copper foil, aluminum alloy foil, and composite collector, etc., may be used. The anode active material layer includes an anode active material, and the anode active material is not particularly limited, and any anode active material in the art may be used. For example, at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon carbon, lithium titanate, and the like may be included.
The substrate of the separator of the present application includes, but is not limited to, at least one selected from Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), Polyimide (PI), or aramid. For example, the polyethylene includes at least one component selected from the group consisting of high density polyethylene, low density polyethylene, and ultra high molecular weight polyethylene. Particularly polyethylene and polypropylene, which have excellent effects on preventing short circuits and can improve the stability of an electrochemical device through a turn-off effect. The substrate may be a single layer structure or a multi-layer composite structure of a mixture of a plurality of kinds, and has a thickness of 3 to 20 μm.
A second aspect of the present application provides an electronic device comprising an electrochemical device as described in the above-described embodiments of the present application.
The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, a lithium ion capacitor, and the like.
The process for preparing the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited. For example, the electrochemical device may be manufactured by the following process: the positive electrode, the isolating membrane and the negative electrode are stacked in sequence, and are placed into the shell after being wound, folded and the like according to needs, electrolyte is injected into the shell and the shell is sealed, wherein the isolating membrane is the isolating membrane provided by the application. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the case as necessary to prevent a pressure rise and overcharge/discharge inside the electrochemical device. The positive pole of this application can refer to positive pole piece, and the negative pole can refer to negative pole piece.
The application provides an electrochemical device and electron device, including positive pole piece, negative pole piece, barrier film and electrolyte, the barrier film sets up between positive pole piece and negative pole piece, and barrier film wherein includes the substrate and is located the at least one functional layer on the surface of substrate, and this application satisfies between A through the thickness H of control functional layer and the liquid retaining coefficient of electrolyte: A/H is more than or equal to 0.048 and less than or equal to 4.5, so that a large amount of electrolyte can be stored in the isolating membrane, the low-temperature circulation interface between the electrode pole piece and the isolating membrane is improved, the internal resistance of the electrochemical device is reduced, and the high-rate circulation performance of the electrochemical device under the low-temperature condition is improved.
In one embodiment of the present application, as shown in fig. 1, a separator in a lithium ion battery includes a separator substrate 1, and a first functional layer 2 and a second functional layer 3 respectively disposed on both surfaces of the separator substrate 1.
In one embodiment of the present application, as shown in fig. 2, a third functional layer 4 is provided between the first functional layer 2 and the substrate 1.
In one embodiment of the present application, a third functional layer 4 is provided between the second functional layer 3 and the substrate 1, as shown in fig. 3.
In one embodiment of the present application, as shown in fig. 4, a third functional layer 4 is provided between the first functional layer 2 and the substrate 1, and between the second functional layer 3 and the substrate 1.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "part" and "%" are based on mass.
The test method and the test equipment are as follows:
and (3) testing the thickness of the functional layer:
1) under the room temperature environment, detaching the isolating film with the functional layer and the pole piece facing the functional layer from the lithium ion battery (for example, the isolating film and the positive pole piece are kept in an adhesion state), and wiping off the residual electrolyte on the surfaces of the isolating film and the pole piece by using dust-free paper (Clearom wipe-0609);
2) cutting the isolating film and the electrode plate under plasma to obtain the cross section of the isolating film and the electrode plate;
3) observing the cross section of the electrode pole piece obtained in the step 2) under a Scanning Electron Microscope (SEM), testing the thickness of the functional layer, testing at least 15 different points at intervals of 2-3 mm between adjacent test points, and recording the average value of all the test points as the thickness of the functional layer.
Or
Selecting a fresh isolating membrane which is not made into a lithium ion battery in a room temperature environment, cutting the isolating membrane by using plasma to obtain a cross section of the isolating membrane, observing the obtained cross section of the isolating membrane under a Scanning Electron Microscope (SEM), testing the thickness of a functional layer, testing at least 15 different points at intervals of 2-3 mm between adjacent test points, and recording the average value of all the test points as the thickness of the functional layer.
And (3) testing the liquid retention coefficient of the electrolyte:
calculating the electrolyte retention coefficient of the lithium ion battery according to the following expression:
the liquid retention coefficient is the electrolyte retention amount/first-circle discharge specific capacity of the lithium ion battery.
Testing the liquid retention amount of the electrolyte: weighing 1 lithium ion battery as m0, then disassembling the lithium ion battery, centrifugally separating out electrolyte, putting the disassembled aluminum-plastic film, isolating film, positive pole piece, negative pole piece and tab into acetonitrile solution, then taking out the aluminum-plastic film, isolating film, positive pole piece, negative pole piece and tab, drying, weighing as m1, and keeping the electrolyte solution at m0-m 1.
Testing the adhesive force between the isolating film and the electrode pole piece:
adopting national standard GB/T2790-: cutting the compounded sample into strips of 15mm multiplied by 54.2mm at the temperature of 85 ℃, the pressure of 1Mpa and the hot pressing time of 85s (seconds), and testing the adhesive force between the isolating membrane and the anode pole piece or the cathode pole piece according to a 180-degree stripping test standard.
Polymer average particle size test:
the average particle size of the polymer was measured using a scanning electron microscope.
Testing the direct current internal resistance increase rate (DCR) increase rate of the lithium ion battery:
1) fully charging the lithium ion battery to 4.45V at a current density of 10mA/g, standing for 10min, discharging to 3.0V at a current density of 10mA/g, and recording the obtained capacity C;
2) standing for 5min, charging to 4.45V at constant current of 0.7C, and then charging to current of less than 0.05C at constant voltage of 4.45V;
3) standing for 10min, and discharging for 3h with 0.1C discharge current;
4) discharging for 1 second with the discharge current of 1C, collecting direct current resistance data before and at the cycle of 100 th circle, taking an average value before and after the cycle, and solving the average growth rate according to the following expression:
the average DCR increase rate for 500 cycles is (dc resistance of 500 th cycle-dc resistance before cycle)/dc resistance before cycle x 100%.
The average DCR increase rate per cycle of 500 cycles-500 cycles DCR average increase rate/500 cycles.
Testing the cycle capacity retention rate of the lithium ion battery:
the test environment temperature is 12 ℃, and the comparative example and the example adopt the same charging process: and (3) charging the formed lithium ion battery to 4.45V at a constant current of 3C multiplying power, then charging at a constant voltage until the current is less than or equal to 0.05C, standing for 5min after the battery is fully charged, and then discharging to 3.0V at a constant current of 1C multiplying power, wherein the process is a charging and discharging cycle process, the discharging capacity of the first cycle is recorded, the charging and discharging cycle is repeated for 500 times, and the discharging capacity of the 500 th cycle is recorded.
The cycle capacity retention rate (discharge capacity at 500 th cycle/discharge capacity at first cycle) × 100%.
Testing the high-temperature storage performance of the lithium ion battery:
the high-temperature storage properties of each of the example and comparative cells were measured according to the following procedures: the lithium ion battery was allowed to stand at 25 ℃ for 30 minutes, then was constant-current charged to 4.45V at a rate of 0.5C, was constant-voltage charged to 0.05C at 4.45V, was allowed to stand for 5 minutes, and after being stored at 80 ℃ for 7 hours, the thickness of the battery was measured, and the expansion rate of the thickness of the battery was calculated by the following formula: thickness expansion rate ═ thickness after storage-thickness before storage)/thickness before storage ] × 100%.
Example 1
<1-1. preparation of electrolyte solution >
Mixing Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC) and chain carboxylic acid ester (such as Ethyl Acetate (EA)) in an argon atmosphere glove box with a water content of less than 10ppm to obtain a nonaqueous organic solvent, and adding lithium hexafluorophosphate (LiPF) to the nonaqueous organic solvent6) And fluoroethylene carbonate (FEC).
In table 1, based on the total mass of the electrolyte, the mass percentage of DEC is 40%, the mass percentage of EA is 20%, and the mass percentage of FEC is 5%; mixing EC and PC in the electrolyte according to the mass ratio of 1: 1; LiPF6The concentration of (2) is 1 mol/L.
<1-2. preparation of separator >
<1-2-1. preparation of third functional layer >
Mixing aluminum oxide (Al)2O3Average particle size of 2 μm) was dispersed in N-methylpyrrolidone (NMP) to form a slurry having a solid content of 50%, and then the resulting slurry was uniformly coated on one side of a separator film substrate (e.g., polyethylene, thickness of 5 μm, average pore size of 0.073 μm, porosity of 26%) by a micro gravure coating method, and dried to obtain a third functional layer having a thickness of 0.5 μm. The thickness of the third functional layer can be controlled by controlling the weight of the slurry per unit area.
<1-2-2. preparation of second functional layer >
Adding distilled water into a reaction kettle, starting stirring, introducing nitrogen to remove oxygen for 2 hours, and adding the following monomers into the reaction kettle according to a mass ratio of 80: 10: heating styrene, butyl acrylate and acrylonitrile in an inert atmosphere to 65 ℃ in the inert atmosphere, keeping the temperature constant, adding 20% ammonium persulfate solution as an initiator to start reaction, taking out a precipitate after the reaction lasts for 22 hours, and adding alkali liquor to neutralize the pH value to 6.5. Wherein the mass ratio of distilled water, monomer and initiator is 89.5: 10: 0.5. After the reaction, the reaction product is filtered, washed, dried, crushed, sieved and the like to obtain a second polymer with the average particle size of 3 microns.
Adding 91g of the prepared second polymer into a stirrer, adding 0.5g of sodium carboxymethylcellulose, uniformly stirring, adding 8.5g of first compound dimethyl siloxane, adding deionized water, stirring, adjusting the viscosity of the slurry to be 100mPa & s and the solid content to be 12%, uniformly coating the prepared slurry on the surface of the isolating membrane substrate which is not coated with the third functional layer, and drying to obtain the second functional layer, wherein the thickness of the second functional layer is 5 micrometers, and the mass of the second functional layer is 3mg/5000mm2And obtaining the isolating membrane.
<1-2-3. preparation of first functional layer >
Vacuumizing a reaction kettle, vacuumizing nitrogen to replace oxygen, and adding deionized water, vinylidene fluoride (VDF), an initiator, namely diisopropylbenzene hydroperoxide, an emulsifier perfluoroalkyl carboxylate and a chain transfer agent namely isopropanol into the reaction kettle containing a stirrer until the pressure of the reaction kettle is 3.5MPa, wherein the deionized water is 7 times of the mass of the vinylidene fluoride monomer, the initiator accounts for 0.2 percent of the mass of the vinylidene fluoride monomer, the emulsifier accounts for 0.5 percent of the mass of the vinylidene fluoride monomer, and the chain transfer agent accounts for 5 percent of the mass of the vinylidene fluoride monomer. And then heating to 60 ℃, rotating the stirrer at a speed of 80r/min, starting a polymerization reaction, continuously adding the vinylidene fluoride monomer, keeping the pressure of the reaction kettle at 3.5MPa, stopping the reaction until the solid content of the emulsion in the reactor reaches 25%, recovering unreacted monomer, discharging the polymer emulsion, centrifuging, washing and drying to obtain a first polymer with the average particle size of 1 mu m.
Adding 90g of the first polymer polyvinylidene fluoride (PVDF) into a stirrer, adding 10g of the first auxiliary adhesive acrylonitrile, and uniformly stirring and mixingUniformly mixing, adding deionized water, stirring, adjusting the viscosity of the slurry to 40mPa & s and the solid content to 5%, uniformly coating the prepared slurry on a third functional layer, and drying to obtain a first functional layer, wherein the thickness of the first functional layer is H1 and the mass of the first functional layer is 5mg/5000mm2。
<1-3. preparation of Positive electrode sheet >
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing polyvinylidene fluoride (PVDF) and conductive carbon black (SP) according to the mass ratio of 96.7: 1.7: 1.6, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 mu m, drying at 90 ℃, cold-pressing to obtain a positive pole piece with the thickness of a positive active material layer of 100 mu m, and repeating the steps on the other surface of the positive pole piece to obtain the positive pole piece with the positive active material layer coated on two surfaces. Cutting the positive pole piece into the specification of 74mm multiplied by 867mm, and welding the pole lugs for later use.
<1-4. preparation of negative electrode sheet >
Mixing the negative active material artificial graphite, Styrene Butadiene Rubber (SBR) and carboxymethyl cellulose (CMC) according to the mass ratio of 98: 1, then adding deionized water as a solvent, blending into slurry with the solid content of 70%, and uniformly stirring. And uniformly coating the slurry on one surface of a copper foil with the thickness of 8 mu m, drying at 110 ℃, cold-pressing to obtain a negative pole piece with the negative active material layer of 150 mu m in thickness and with the single-surface coated with the negative active material layer, and repeating the coating steps on the other surface of the negative pole piece to obtain the negative pole piece with the double-surface coated with the negative active material layer. Cutting the negative pole piece into a size of 74mm multiplied by 867mm, and welding a pole lug for later use.
<1-5. preparation of lithium ion Battery >
And (3) stacking the prepared positive pole piece, the prepared isolating membrane and the prepared negative pole piece in sequence, so that the isolating membrane is positioned between the positive pole piece and the negative pole piece to play an isolating role, wherein one surface of the isolating membrane with the first functional layer faces the negative pole piece, and one surface of the isolating membrane with the second functional layer faces the positive pole piece, and winding to obtain the electrode assembly. And (3) putting the electrode assembly into an aluminum-plastic film packaging bag, dehydrating at 80 ℃, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
In examples 1 to 23 and comparative examples 1 to 2, the preparation steps of < electrolyte preparation >, < positive electrode preparation >, < negative electrode preparation >, < separator preparation > and < lithium ion battery preparation > were the same as in example 1, the third functional layer was disposed between the first functional layer and the substrate in examples 1 to 19, 21 to 23 and 1 to 2, and the third functional layer was disposed on the side facing the negative electrode in example 19, and the change of the relevant preparation parameters and the performance data were as shown in table 1:
TABLE 1
"/" indicates the absence of the substance or composition.
As can be seen from examples 1 to 20, example 22, example 23 and comparative examples 1 to 3, the DCR growth rate of the lithium ion battery with the A/H ratio relationship of the application is obviously reduced; as can be seen from examples 1 to 23 and comparative examples 1 to 3, the capacity retention rate thereof was significantly improved, indicating that the lithium ion battery of the present application has excellent large-rate cycle performance at low temperature. As can be seen from examples 1 to 13 and comparative example 1, as the thickness of the first functional layer H1 increases, the liquid retention coefficient of the separator for the electrolyte gradually increases, and a high liquid retention coefficient is favorable for the transmission of lithium ions at negative and very low temperatures, and improves the negative electrode interface in the low-temperature cycle process, thereby reducing the impedance increase in the cycle process and gradually improving the low-temperature cycle performance of the lithium ion battery; as can be seen from examples 14 to 19 and comparative example 1, since the third functional layer is mainly used for physically isolating the positive electrode and the negative electrode, the low-temperature cycle performance of the lithium ion battery is not greatly affected as the thickness of the third functional layer increases; as can be seen from examples 20 to 23 and comparative examples 1 to 3, the combination of H1 and the liquid retention coefficient is required to significantly improve the low-temperature cycle performance of the lithium ion battery, and the thickness of the second functional layer has little influence on the low-temperature cycle performance of the lithium ion battery.
Examples 24 to 40
In table 2, the thickness of the first functional layer is 2 μm, the thickness of the second functional layer is 5 μm, the third functional layer is disposed between the substrate and the first functional layer and is 0.5 μm, the liquid retention coefficient of the electrolyte is 1.51mg/mAh, EC and PC in the electrolyte are mixed according to the mass ratio of 1:1, and then DEC, chain carboxylate and FEC are added according to the following ratio, and the change of the relevant preparation parameters and the performance data are shown in table 2:
TABLE 2
As can be seen from examples 24 to 40, the content of the chain carboxylic ester and fluoroethylene carbonate in the electrolyte also has a certain influence on the retention coefficient of the electrolyte, but if the content of the chain carboxylic ester and fluoroethylene carbonate and the ratio of the chain carboxylic ester and fluoroethylene carbonate are within the range of the present application, a lithium ion battery having excellent high rate cycle performance at low temperature can be obtained. It can be seen from examples 25 to 30 and example 36 that the content of chain-like carboxylate (e.g., ethyl acetate) in the electrolyte is increased, the lithium ion conductivity of the electrolyte is high at low temperature, which is beneficial to improving the low-temperature cycle interface between the pole piece and the isolating membrane, and further improving the low-temperature cycle performance of the lithium ion battery, and it can be seen from examples 24 and 25 that the content of ethyl acetate is further increased, although the cycle capacity retention rate of the lithium ion battery is improved, the dissociation of lithium salt is affected, and the low-temperature cycle performance is affected; from examples 31 to 36, it can be seen that the content of fluoroethylene carbonate in the electrolyte is increased, the protection of the negative electrode in the electrolyte is stronger, the interface of the negative electrode under low-temperature cycling can be improved, and the low-temperature cycling performance of the lithium ion battery is improved, and in addition, both ethyl acetate and FEC affect the high-temperature storage performance of the battery, so the influence of the contents of both can be comprehensively considered.
Examples 41 to 46
The procedure of example 35 was repeated, except that 1, 3-propanesultone of the formula (1-8) was added to the electrolyte prepared in example 35, and the content of 1, 3-propanesultone in the electrolyte was as shown in Table 3.
In examples 41 to 46, the production steps of < electrolyte preparation >, < positive electrode preparation >, < negative electrode preparation >, < separator preparation > and < lithium ion battery preparation > were the same as in example 35, and the changes in the relevant production parameters and the performance data are shown in table 3:
| TABLE 3 | Content of sultone Compound | DCR growth rate | Capacity retention rate |
| Example 35 | 0.00％ | 31.82％ | 74.80％ |
| EXAMPLE 41 | 0.01％ | 30.95％ | 75.40％ |
| Example 42 | 0.10％ | 29.65％ | 76.70％ |
| Example 43 | 1.00％ | 28.32％ | 79.50％ |
| Example 44 | 3.00％ | 28.10％ | 80.20％ |
| Example 45 | 5.00％ | 27.95％ | 79.10％ |
| Example 46 | 8.00％ | 27.76％ | 77.20％ |
From example 35 and examples 41 to 46, it can be seen that 1, 3-propane sultone generally affects the DCR increase rate and capacity retention rate of the lithium ion battery, 1, 3-propane sultone can form lithium sulfate at the interface of the positive electrode, and lithium sulfate can reduce the interface impedance and inhibit the electrolyte from further side reactions. When the content of the 1, 3-propane sultone in the electrolyte is within the range of the application, the DCR growth rate of the lithium ion battery can be further reduced, and the high-rate cycle performance of the lithium ion battery at low temperature is improved. From example 35 and examples 41 to 44, it can be seen that the increase of the content of 1, 3-propane sultone enhances the protection of the positive electrode of the lithium ion battery and improves the low-temperature cycle performance, and from examples 45 and 46, the addition of a large amount of 1, 3-propane sultone affects the electrolyte kinetics and thus the low-temperature cycle.
Examples 47 to 59
Example 43 was repeated, except that adiponitrile of formula (2-2) and 1,3, 6-hexanetricarbonitrile of formula (3-1) were added to the electrolyte prepared in example 43, and the amounts of adiponitrile and 1,3, 6-hexanetricarbonitrile in the electrolyte were as shown in Table 4.
In examples 47 to 59, the production steps of < electrolyte preparation >, < positive electrode preparation >, < negative electrode preparation >, < separator preparation > and < lithium ion battery preparation > were the same as in example 43, and the changes in the relevant production parameters and the performance data are shown in table 4:
TABLE 4
As can be seen from examples 47 to 59, dinitrile compounds and trinitrile compounds also generally affect the DCR growth rate and capacity retention of lithium ion batteries. Dinitrile and trinitrile can stabilize the high-valence cobalt in lithium cobaltate under the high voltage through chemisorption, and the combined action of dinitrile and trinitrile can reduce its catalytic oxidation to electrolyte, reduce the side reaction of positive pole side in the high voltage cyclic process, and then reduce the impedance increase in the cyclic process, and the content of dinitrile compound and trinitrile compound in the electrolyte is in this application scope, just can further reduce lithium ion battery's DCR growth rate, improves the big multiplying power cycling performance of lithium ion battery at low temperature. The dinitrile compound and the trinitrile compound can protect the structure of the anode in the low-temperature circulation process through chemical adsorption, and the dinitrile compound and the trinitrile compound have different structures and can form complementation in space, so that the low-temperature circulation performance of the lithium ion battery is improved.
In examples 60 to 65, the production steps of < electrolyte preparation >, < positive electrode preparation >, < negative electrode preparation >, < separator preparation > and < lithium ion battery preparation > were the same as in example 58 except that lithium difluorophosphate was further added to the electrolyte, and the change in the relevant production parameters and the performance data are shown in table 5:
TABLE 5
| Lithium difluorophosphate content | DCR growth rate | Capacity retention rate | |
| Example 58 | 0 | 28.76％ | 81.40％ |
| Example 60 | 0.01％ | 28.61％ | 81.70％ |
| Example 61 | 0.10％ | 27.50％ | 82.30％ |
| Example 62 | 0.50％ | 27.23％ | 84.20％ |
| Example 63 | 0.6％ | 28.10％ | 82.40％ |
| Example 64 | 0.8％ | 28.37％ | 81.20％ |
| Example 65 | 1.00％ | 29.70％ | 79.80％ |
As can be seen from examples 60 to 65, lithium difluorophosphate generally also affects the DCR growth rate and capacity retention of lithium ion batteries. Lithium difluorophosphate can form a film on a negative electrode, a negative electrode low-temperature cycle interface in the lithium ion battery is improved, when the content of the lithium difluorophosphate in the electrolyte is within the range of the application, the DCR growth rate of the lithium ion battery can be further reduced, and the high-rate cycle of the lithium ion battery at low temperature is improved.
Examples 66 to 72
The procedure of example 35 was repeated, except that in the preparation of the electrolytic solution, the chain carboxylate, the sultone compound, the dinitrile compound and the trinitrile compound were replaced with those shown in table 6.
In examples 66 to 72, the production steps of < electrolyte preparation >, < positive electrode preparation >, < negative electrode preparation >, < separator preparation > and < lithium ion battery preparation > were the same as in example 35, and the changes in the relevant production parameters and the performance data are shown in table 6:
TABLE 6
"/" indicates the absence of the substance or composition.
As can be seen from examples 66 to 72, the kinds of chain carboxylates, sultone compounds, dinitrile compounds, and trinitrile compounds also generally affect the DCR growth rate and capacity retention rate of the lithium ion battery. When the types of chain carboxylic ester, sultone compound, dinitrile compound and trinitrile compound are in the range of the application, the lithium ion battery with better comprehensive performance can be obtained.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. An electrochemical device comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte, wherein the isolating membrane is arranged between the positive pole piece and the negative pole piece and comprises a base material and a functional layer positioned on at least one surface of the base material, wherein the electrochemical device meets the condition that A/H is more than or equal to 0.048 and less than or equal to 4.5, and H [ mu ] m is the thickness of the functional layer; a mg/mAh is the liquid retention coefficient of the electrolyte.
2. The electrochemical device of claim 1, wherein at least one of conditions (a) or (b) is satisfied:
(a)1.2≤A≤4.5；
(b)1≤H≤25。
3. the electrochemical device according to claim 1, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, a side of the substrate facing the negative electrode active material layer is provided with a first functional layer, and at least one of conditions (c) to (f) is satisfied:
(c) the thickness of the first functional layer is H1 mu m, and H1 is more than or equal to 2 and less than or equal to 15;
(d) the first functional layer comprises a first polymer having an average particle diameter of 1.5 to 15 μm;
(e) the first functional layer comprises a first polymer comprising at least one of a homopolymer or copolymer of vinylidene fluoride, hexafluoropropylene, ethylene, propylene, vinyl chloride, chloropropene, acrylic acid, an acrylate, styrene, butadiene, and acrylonitrile;
(f) the mass of the first functional layer is 2mg/5000mm2To 10mg/5000mm2。
4. The electrochemical device according to claim 1, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, and a second functional layer is disposed on a surface of the substrate facing the positive electrode active material layer, and at least one of the conditions (g) to (j) is satisfied:
(g) the thickness of the second functional layer is H2 mu m, and H2 is more than or equal to 0.5 and less than or equal to 10;
(h) the adhesion between the separator and the negative electrode active material layer is N1, the adhesion between the separator and the positive electrode active material layer is N2, and N1 is less than N2;
(i) the mass of the second functional layer is 0.3mg/5000mm2To 5mg/5000mm2；
(j) The second functional layer comprises a second polymer comprising at least one of a homopolymer or copolymer of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, ethyl methacrylate, butyl methacrylate, ethylene, chlorostyrene, fluorostyrene, methylstyrene, acrylonitrile, or methacrylonitrile.
5. The electrochemical device according to claim 1, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, a first functional layer is provided on a side of the substrate facing the negative electrode active material layer, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, a second functional layer is provided on a side of the substrate facing the positive electrode active material layer, a third functional layer is provided between the substrate and at least one of the first and second functional layers, the third functional layer comprises inorganic particles, and at least one of the conditions (k) to (l) is satisfied:
(k) the third functional layer has a thickness of 0.2 to 6 μm;
(l) The inorganic particles include at least one of alumina, boehmite, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, magnesium hydroxide, magnesium oxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or silicon nitride.
6. The electrochemical device according to claim 1, wherein the electrolyte comprises chain carboxylic ester and fluoroethylene carbonate, wherein the chain carboxylic ester is present in an amount of X% by mass and the fluoroethylene carbonate is present in an amount of Y% by mass based on the total mass of the electrolyte, and the relationship between X and Y satisfies: X/Y is more than or equal to 0.5 and less than or equal to 30.
7. The electrochemical device according to claim 6, wherein the chain carboxylic acid ester includes a compound represented by structural formula (1):
wherein R is1Selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms, a substituted or unsubstituted chain alkenyl group having 2 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 15 carbon atoms, R2Selected from substituted or unsubstituted alkyl groups having 1 to 5 carbon atoms, substituted or unsubstituted chain alkenyl groups having 2 to 6 carbon atoms, and substituted or unsubstituted aryl groups having 6 to 15 carbon atoms; when each group is substituted, the substituent is selected from hydrogen atom, halogen atom, hydroxyl, methyl, ethyl, propyl, butyl, vinyl, phenyl, phenoxy; based on the total mass of the electrolyte, the mass percentage of the chain carboxylic ester is 5-60%.
8. The electrochemical device of claim 1, wherein the electrolyte further comprises at least one of a sultone compound, a dinitrile compound, a trinitrile compound, or lithium difluorophosphate; based on the total mass of the electrolyte, the mass percentage of the sultone compound is 0.01-6%, the mass percentage of the dinitrile compound is 0.1-10%, the mass percentage of the trinitrile compound is 0.1-5%, and the mass percentage of the lithium difluorophosphate is 0.01-1%.
9. The electrochemical device according to claim 8, wherein the sultone compound includes any one of the following formulas (1-1) to (1-8):
the dinitrile compound includes any one of the following formulae (2-1) to (2-4):
the trinitrile compound includes any one of the following formulae (3-1) to (3-3):
10. an electronic device comprising the electrochemical device of any one of claims 1-9.
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